Best way to access my NAS using Tailscale without speeds suffering?

Hey all, I'm pretty new to this whole thing, so apologies if I get anything wrong, but I'm hoping to pick some of your brains as to how to best architect my network. I've been using a NAS I built running TrueNAS for a while now, and I haven't had any issues with it. I mainly access it from my main PC, but the problem is I move my main PC around a lot and frequently use it off of my local network. Up until recently, I've just been using Tailscale to accommodate this. I have it installed on my NAS and my PC and I just map the network drive in windows to the Tailscale IP. This has worked well and I've been able to access the NAS at the "maximuim" speed of whatever network I'm on.

Recently though, I upgraded my NAS to 2.5gb networking. I just have my PC and the NAS connected to a 2.5gb switch, and I expected it to work without issue. As some of you have probably guessed though, in practice, I was only getting about 1.6gb transfers in practice. This seemed sus to me, so I did some digging, and sure enough, it's a tailscale issue. As best I understand it's something along the lines of it being an overhead issue with the tunnel, but I won't pretend to understand the specifics more than that.

So I know I need to take Tailscale out of the equation when on my local network, but I am having an immense amount of trouble trying to figure out how exactly to do this. It's very important to me that I just have a single mapped network drive in windows, that I can access seamlessly over SMB. I don't really even care all that much about remote access (although it is nice to have), but in my experience windows has a complete stroke when one of your network drives are offline, so I'm really trying to avoid that if possible.

So I need a way for windows to use the local IP address of the NAS when I'm on my local network, and use Tailscale's IP address when I'm not. I know the solution to this probably lies in DNS somewhere, but so far nothing I have tried has actually worked and somehow the Tailscale interface always ends up getting priority again somehow. I've tried setting up a DNS address on my router and in windows, and I think at this point I've gotten everything kind of tangled up lol. My latest attempt was to let the NAS act as a subnet router for Tailscale, but despite working initially that somehow broke almost immediately again too.

Any advice would be appreciated! I'm sure I can't be the only person with this issue so what is typically the best way to approach the architecture for something like this. Thanks!